May 14, 2010

Earliest Birds Were Poor Flyers

The earliest birds may have had feathers, but they were not strong enough to carry the winged creatures in flight, researchers revealed Thursday.

Recent fossil discoveries show that feathers on some of the early birds, including Confuciusornis and Archaeopteryx, were too weak to support the birds in flight.

While modern birds have feathers with a strong central shaft that is hollow to reduce weight, the earliest-known birds had feathers that were much thinner and more frail.

Robert Nudds of the University of Manchester and Gareth Dyke of University College Dublin studied the fossil records and determined that even if the feather shafts were solid, they would still have been barely strong enough to allow gliding.

Archaeopteryx thrived during the Late Jurassic Period about 145 million years ago and Confuciusornis in the Early Cretaceous Period about 100 to 120 million years ago.

It is widely believed in the paleontology world that the first birds evolved from small, feathered dinosaurs. One theory is that small dinosaurs living in trees initially used feathers to control their descent like a parachute, then glided through the forest canopy and eventually flapped their wings to achieve flight.

Unfortunately, researchers cannot tell from the fossil remains if the feather shafts were hollow, like modern birds, or solid.

If the feathers of these early birds were in fact hollow, the thin shafts would have buckled like a straw if the animals had tried vigorous flapping, according to Nudds and Dyke. "If solid, the feathers would have snapped off," Nudds countered.

"Some thrust generation by these fossil birds cannot be discounted, but the vigorous flapping flight of modern birds is highly unlikely," the researchers concluded.

"If Archaeopteryx and Confuciusornis were arboreal dwellers, which is suggested by my data, then it also suggests that avian flight originated in the trees and not on the ground," Nudds said.

"Fossil wings that superficially resemble those of existing birds don't necessarily indicate flapping flight ability," concluded Nudds, who added that the origin of avian flapping flight is likely to be more recent than previously thought.

Archaeopteryx is believed to be an intermediary form between reptiles and birds. Unlike modern birds, it had a full set of teeth, a long bony tail and three claws on each wing. It was the size of a small chicken.

Confuciusornis was a crow-sized bird that had a small triangular snout and, unlike Archaeopteryx, lacked any teeth.

Their study is published in May 14th issue of Science.

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Image Caption: The feathers of Confuciusornis, a 100"“million-year-old prehistoric bird, could probably not sustain vigorous flapping flight. Credit: Carnegie Museum of Natural History